Link selection for device-to-device communications

ABSTRACT

The disclosure generally relates to negotiating a best device-to-device (D2D) radio access technology (RAT) to use in a D2D connection. In particular, two wireless devices that correspond to potential D2D peers may exchange respective radio configurations according to a D2D coexistence protocol to mutually negotiate the “best” RAT to use in the D2D connection, wherein the exchanged radio configurations may comprise at least radio capabilities and coexistence states (e.g., in-device and/or cross-device coexistence states) associated with the respective wireless devices. The potential D2D peers may then negotiate one or more compatible RATs that are available to use in the D2D connection according to at least the radio capabilities and the in-device and cross-device coexistence states exchanged therebetween. As such, the two wireless devices may then establish one or more D2D connections using the negotiated compatible RAT(s).

TECHNICAL FIELD

The various aspects and embodiments described herein generally relate todevice-to-device (D2D) or peer-to-peer (P2P) communications, and inparticular, to negotiating a best D2D/P2P radio access technology to usein a D2D/P2P connection according to one or more policies based onperformance, power, coexistence, preference, and/or other criteria.

BACKGROUND

Wireless communication systems have developed through variousgenerations, including a first-generation analog wireless phone service(1G), a second-generation (2G) digital wireless phone service (includinginterim 2.5G and 2.75G networks) and third-generation (3G) andfourth-generation (4G) high speed data/Internet-capable wirelessservices. There are presently many different types of wirelesscommunication systems in use, including Cellular and PersonalCommunications Service (PCS) systems. Example cellular systems includethe cellular Analog Advanced Mobile Phone System (AMPS), digitalcellular systems based on Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), the Global System for Mobile access (GSM) TDMA variation, andnewer hybrid digital communication systems that use both TDMA and CDMAtechnologies. More recently, Long Term Evolution (LTE) has beendeveloped as a wireless communications protocol for wirelesscommunication of high-speed data for mobile phones and other dataterminals. LTE is based on GSM, and includes contributions from variousGSM-related protocols (e.g., Enhanced Data rates for GSM Evolution(EDGE)) and Universal Mobile Telecommunications System (UMTS) protocols(e.g., High-Speed Packet Access (HSPA)).

Accordingly, communications systems and devices are becomingincreasingly diverse with new technological advancements. Manycommunications devices can now support various different communicationstechnologies and protocols. Indeed, not only can various communicationsdevices operate in a communications system (e.g., over a networkinfrastructure), many communications device may communicate with oneanother using direct device-to-device (D2D) communications when locatedin sufficient proximity to one another. For example, communicationsdevices that support the Wi-Fi Direct standard may connect to each othervia a D2D connection and communicate at typical Wi-Fi speeds withminimal setup and without requiring any intermediate wireless accesspoint. Furthermore, the LTE Direct standard uses licensed spectrum andthe LTE physical layer to provide a scalable and universal frameworkthrough which equipped communications devices can discover and connectto proximate peers and thereby establish D2D connections within rangesup to approximately 500 meters, whereas Wi-Fi direct tends to requirethe devices to be in closer proximity. Further still, wireless devicesoperating in the “Bluetooth” wireless communication spectrum can engagein D2D communication over relatively short distances, with an operatingrange ranging from a few meters to a few tens of meters, and near-fieldcommunication (NFC) technology refers to an open-platform,standard-based, short-range, high-frequency wireless communicationtechnology that enables a bidirectional information exchange betweenNFC-equipped devices via magnetic field induction over very smalldistances (e.g., about ten centimeters). In any particular device, oneor more D2D connections may be active at a given time, including at atime when the device may have a concurrent connection with one or moreinfrastructure elements (e.g., a WLAN access point, a cellular basestation, etc.).

As such, D2D communications are becoming increasingly popular andmultiple schemes already exist (with more continuing to emerge) becauseD2D communications can be faster, more efficient, more private, orotherwise advantageous to end users. Moreover, network operators and endusers can realize substantial benefits from using D2D communicationsrather than communicating over a network infrastructure, especially whentwo or more devices seeking to communicate are located in proximity toone another and can establish a D2D connection with reasonably goodquality. However, current D2D schemes typically select one technology(e.g., Wi-Fi Direct) that may be fastest or most ubiquitous. However,the default technology selection to use in a D2D connection may beunavailable or suboptimal under certain circumstances. For example,certain technologies may be incompatible across devices from differentmanufacturers, provide insufficient performance with respect to aparticular communication session (e.g., a large file to be transferred),and/or cause coexistence issues in the devices that communicate over theD2D connection, including in-device and/or cross-device coexistenceissues.

More particularly, as mentioned above, many wireless devices includemultiple radios that each support a different radio access technology(RAT) that can be used to transmit and receive data. For example, theRATs that can be supported on a multi-radio device may include UMTS,GSM, CDMA2000, WiMAX, WLAN (e.g., Wi-Fi), LTE, and the like, and themulti-radio device may further have different radios that each support adifferent D2D RAT, which may include NFC, Bluetooth, Wi-Fi Direct, LTEDirect, and the like. Accordingly, an example multi-radio device mayhave multiple radios that operate simultaneously to provide variousdifferent functions. While the different radios may provide usefulfunctionalities to a user, inclusion in a single device may give rise toin-device coexistence issues where one radio may interfere with anotherradio through radiative, conductive, resource collision, and/or otherinterference mechanisms. Furthermore, D2D communications may createcross-device coexistence issues through similar interference mechanismsdue at least in part to the proximity between the devices communicatingover the D2D connection. For example, the LTE uplink channel is adjacentto the industrial scientific and medical (ISM) band and may causeinterference with Bluetooth and some wireless LAN (WLAN) channels thatfall within the ISM band. In some instances, a Bluetooth error rate canbecome unacceptable when LTE is active in some channels within Band 7 oreven Band 40 even though there may not be a significant degradation toLTE because simultaneous operation with Bluetooth can disrupt voiceservices terminating in a Bluetooth headset, which may be unacceptableto consumers.

Accordingly, solutions to select an optimal RAT to use in a D2Dconnection to mitigate coexistence issues and meet performancerequirements are needed.

SUMMARY

The following presents a simplified summary relating to one or moreaspects and/or embodiments disclosed herein. As such, the followingsummary should not be considered an extensive overview relating to allcontemplated aspects and/or embodiments, nor should the followingsummary be regarded to identify key or critical elements relating to allcontemplated aspects and/or embodiments or to delineate the scopeassociated with any particular aspect and/or embodiment. Accordingly,the following summary has the sole purpose to present certain conceptsrelating to one or more aspects and/or embodiments relating to themechanisms disclosed herein in a simplified form to precede the detaileddescription presented below.

According to various aspects, in a wireless environment where twowireless devices are located in sufficient proximity to, the twowireless devices may negotiate a best radio access technology (RAT) touse in establishing a D2D connection. For example, in variousembodiments, the two wireless devices may each have multiple wirelessradios, which may include a near-field communication (NFC) radio, awireless wide area network (WWAN) radio, a wireless local area network(WLAN) radio, a Bluetooth radio, and/or other suitable radios. As such,the particular radio(s) that the wireless devices use to communicate maycause in-device coexistence issues and/or cross-device coexistenceissues. For example, in-device coexistence issues may occur at a locallevel within each respective wireless device due to interference orother coexistence impacts that may be caused when the respectivewireless device(s) use more than one radio to communicate atsubstantially the same time. Furthermore, when the wireless devices arewithin sufficient proximity, the radio(s) that the wireless devices useto conduct wireless communication operations may cause cross-devicecoexistence issues. As such, depending on the particular radiosavailable and/or in use at the wireless devices seeking to establish theD2D connection, there may be several factors to consider in choosing thebest RAT to form the D2D connection, including at least the in-devicecoexistence impacts and the cross-device coexistence impacts that such aD2D link may cause. As such, the various aspects and embodimentsdescribed herein may provide various solutions that can be used toidentify the best RAT(s) to use in establishing the D2D connection dueto the possibility that the wireless devices may each support one orseveral RATs that can be used to establish the D2D connection.

For example, according to various aspects, the solutions describedherein may involve a negotiation between two wireless devices to selectthe best RAT and/or multi-radio parameters to use when establishing aD2D connection based on various factors, which may include theparticular radio configurations associated with the wireless devices,the available RAT options that can be used to establish the D2Dconnection, criteria that relate to performance, power, preferences,in-device coexistence impacts, cross-device coexistence impacts, and soon. As such, in various embodiments, the wireless devices may each havea respective coexistence manager and policy database, which the wirelessdevices may use to run a D2D coexistence protocol and thereby mutuallynegotiate the “best” RAT to use in establishing a D2D connection. Forexample, in various embodiments, the D2D coexistence protocol maycomprise the wireless devices exchanging radio configurations and radiocapabilities associated with one another to learn the compatible D2DRATs that can be used to establish the D2D connection (i.e., thepossible RATs that the wireless devices can use to establish the D2Dconnection using locally implemented versions on the respective wirelessdevices) and further to learn a multi-radio coexistence state associatedwith each other (e.g., in-device and cross-device coexistence states).The wireless devices may then mutually negotiate the best RAT toestablish the D2D connection based on the compatible D2D RATs and themulti-radio coexistence state(s) exchanged therebetween, among otherfactors.

According to various aspects, a method for selecting a RAT to use in aD2D connection may comprise requesting, by a first wireless device, aradio configuration from a second wireless device, wherein the requestedradio configuration comprises a coexistence state and one or more radiocapabilities associated with the second wireless device, receiving, atthe first wireless device, the coexistence state and the one or moreradio capabilities from the second wireless device, negotiating one ormore compatible RATs available to use in a D2D connection between thefirst wireless and the second wireless device according to at least thecoexistence state and the one or more radio capabilities received fromthe second wireless device, wherein the negotiating may compriseexchanging in-device and cross-device coexistence states between thefirst wireless device and the second wireless device, and establishingone or more D2D connections between the first wireless device and thesecond wireless device using the negotiated one or more compatible RATs.For example, in various embodiments, negotiating the one or morecompatible RATs may further comprise determining that at least one ofthe compatible RATs causes in-device and/or cross-device interference atone or more of the first wireless device or the second wireless devicebased on the exchanged in-device and cross-device coexistence states,negotiating a modified configuration associated with the at least onecompatible RAT to mitigate the in-device and/or cross-deviceinterference, and adjusting a multi-radio configuration at the firstwireless device according to the negotiated modified configurationassociated with the at least one compatible RAT, wherein the secondwireless device may likewise adjust the radio configuration associatedtherewith according to the modified configuration. Furthermore, invarious embodiments, negotiating the one or more compatible RATs mayfurther comprise determining that one compatible RAT is available to usein the D2D connection between the first wireless and the second wirelessdevice, in which case the one or more D2D connections between the firstwireless device and the second wireless device may comprise one D2Dconnection established according to the one compatible RAT.Alternatively, in response to determining that multiple compatible RATsare available to use in the D2D connection between the first wirelessand the second wireless device, the method may further compriseselecting one or more of the multiple compatible RATs to meet aperformance requirement associated with the D2D connection, which may beperformed according to a priority list that orders the multiplecompatible RATs according to one or more policies that are based on oneor more of a user preference, a device state, or a mobile networkoperator preference.

According to various aspects, a wireless device may comprise multipleradios that each support a different RAT, a transmitter configured totransmit a request to a target peer wireless device, a receiverconfigured to receive a coexistence state and one or more radiocapabilities associated with the target peer wireless device in responseto the transmitted request, and one or more processors configured toexchange in-device and cross-device coexistence states between thewireless device and the target peer wireless device, negotiate one ormore compatible RATs available to use in a D2D connection between thewireless and the target peer wireless device according to the exchangedin-device and cross-device coexistence states, and establish one or moreD2D connections between the wireless device and the target peer wirelessdevice using the negotiated one or more compatible RATs.

According to various aspects, an apparatus may comprise means forrequesting a radio configuration from a target peer wireless device,wherein the requested radio configuration may comprise a coexistencestate and one or more radio capabilities associated with the target peerwireless device, means for receiving the coexistence state and the oneor more radio capabilities from the target peer wireless device, meansfor negotiating one or more compatible RATs available to use in a D2Dconnection with the target peer wireless device according to at leastthe coexistence state and the one or more radio capabilities receivedfrom the target peer wireless device, wherein the means for negotiatingmay comprise means for exchanging in-device and cross-device coexistencestates with the target peer wireless device, and means for establishingone or more D2D connections with the target peer wireless device usingthe negotiated compatible RATs.

According to various aspects, a computer-readable storage medium mayhave computer-executable instructions recorded thereon, whereinexecuting the computer-executable instructions on a wireless devicehaving one or more processors may cause the one or more processors torequest a radio configuration from a target peer wireless device (e.g.,a coexistence state and one or more radio capabilities associated withthe target peer wireless device), receive the coexistence state and theone or more radio capabilities from the target peer wireless device,negotiate one or more compatible RATs available to use in a D2Dconnection with the target peer wireless device according to at leastthe coexistence state and the one or more radio capabilities receivedfrom the target peer wireless device and in-device and cross-devicecoexistence states exchanged with the target peer wireless device, andestablish one or more D2D connections with the target peer wirelessdevice using the negotiated one or more compatible RATs.

Other objects and advantages associated with the aspects and embodimentsdisclosed herein will be apparent to those skilled in the art based onthe accompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of aspects of the disclosure and many ofthe attendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingswhich are presented solely for illustration and not limitation of thedisclosure, and in which:

FIG. 1 illustrates an exemplary wireless communication environment inwhich various aspects and embodiments described herein can function.

FIG. 2 illustrates an exemplary multi-radio wireless device that maysupport one or more device-to-device (D2D) communication technologies,according to various aspects.

FIG. 3 illustrates an exemplary wireless environment in which twowireless devices may negotiate a best D2D radio access technology (RAT)to use in establishing a D2D connection, according to various aspects.

FIG. 4 illustrates example in-device coexistence impacts that may occurin the wireless environment shown in FIG. 3, according to variousaspects.

FIG. 5 illustrates example cross-device coexistence impacts that mayoccur in the wireless environment shown in FIG. 3, according to variousaspects.

FIG. 6 illustrates an example methodology to negotiate a best RAT to usein establishing a D2D connection between two peer devices, according tovarious aspects.

FIG. 7 illustrates another example methodology to negotiate a best RATto use in establishing a D2D connection between two peer devices in amanner that may mitigate in-device and cross-device coexistence impacts,according to various aspects.

FIG. 8 illustrates a block diagram that may correspond to two peerdevices that may engage in D2D communications, according to variousaspects.

DETAILED DESCRIPTION

Various aspects are disclosed in the following description and relateddrawings to show specific examples relating to exemplary embodiments.Alternate embodiments will be apparent to those skilled in the pertinentart upon reading this disclosure, and may be constructed and practicedwithout departing from the scope or spirit of the disclosure.Additionally, well-known elements will not be described in detail or maybe omitted so as to not obscure the relevant details of the aspects andembodiments disclosed herein.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. Likewise, the term “embodiments”does not require that all embodiments include the discussed feature,advantage or mode of operation.

The terminology used herein describes particular embodiments only andshould not be construed to limit any embodiments disclosed herein. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including,” when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., an application specific integrated circuit(ASIC)), by program instructions being executed by one or moreprocessors, or by a combination of both. Additionally, these sequence ofactions described herein can be considered to be embodied entirelywithin any form of computer readable storage medium having storedtherein a corresponding set of computer instructions that upon executionwould cause an associated processor to perform the functionalitydescribed herein. Thus, the various aspects of the disclosure may beembodied in a number of different forms, all of which have beencontemplated to be within the scope of the claimed subject matter. Inaddition, for each of the aspects described herein, the correspondingform of any such aspects may be described herein as, for example, “logicconfigured to” perform the described action.

The techniques described herein may be used in connection with variouswireless communication systems such as CDMA, TDMA, FDMA, OFDMA, andSC-FDMA systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), CDMA2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. CDMA2000 coversIS-2000, IS-95, and IS-856 standards. A TDMA system may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA system may implement a radio technology such as Evolved UTRA(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) is a release of UMTS that uses E-UTRA, which employsOFDMA on the downlink and SC-FDMA on the uplink UTRA, E-UTRA, UMTS, LTE,and GSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). For clarity, certain aspects are described below forLTE, and LTE terminology may be used in much of the description below.

FIG. 1 illustrates an exemplary wireless communication environment inwhich various aspects and embodiments described herein can function. Invarious embodiments, the wireless communication environment 100 shown inFIG. 1 can include a wireless device 110, which can have capabilities tocommunicate with multiple communication systems. For example, thewireless device 110 may have capabilities that support communicationwith one or more cellular networks 120 and/or 130, one or more WLANnetworks 140 and/or 150, a wireless personal area network (WPAN) 160,one or more broadcast networks 170, one or more satellite positioningsystems 180, other systems and/or networks not shown in FIG. 1, or anycombination thereof, wherein the terms “network” and “system” may beused interchangeably in the following description.

In various embodiments, the cellular networks 120 and 130 can each be aCDMA, TDMA, FDMA, OFDMA, single carrier FDMA (SC-FDMA), or othersuitable network. A CDMA network can implement a RAT such as universalterrestrial radio access (UTRA), CDMA2000, etc. UTRA includes widebandCDMA (WCDMA) and other variants of CDMA. Moreover, CDMA2000 coversIS-2000 (CDMA2000 1×), IS-95 and IS-856 (HRPD) standards. A TDMA networkcan implement a RAT such as global system for mobile communications(GSM), digital advanced mobile phone system (D-AMPS), etc. An OFDMAnetwork can implement a RAT such as evolved UTRA (E-UTRA), ultra mobilebroadband (UMB), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc.UTRA and E-UTRA are part of universal mobile telecommunication system(UMTS). 3GPP long term evolution (LTE) and LTE-Advanced (LTE-A) are morerecent releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-Aand GSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). In an aspect, the cellular network 120 can include anumber of base stations 122, which can support bi-directionalcommunication for wireless devices within their coverage. Similarly, thecellular network 130 can include a number of base stations 132 that cansupport bi-directional communication for wireless devices within theircoverage.

WLAN networks 140 and 150 can respectively implement RATs such as IEEE802.11 (Wi-Fi), Hiperlan, etc. The WLAN network 140 can include one ormore access points 142 that can support bi-directional communication.Similarly, the WLAN network 150 can include one or more access points152 that can support bi-directional communication. The WPAN network 160can implement a RAT such as Bluetooth (BT), Bluetooth Low Energy (BTLE),IEEE 802.15, etc. Further, the WPAN network 160 can supportbi-directional communication for various devices such as wireless device110, a headset 162, a computer 164, a mouse 166, or the like.

The broadcast network 170 can be a television (TV) broadcast network, afrequency modulation (FM) broadcast network, a digital broadcastnetwork, etc. A digital broadcast network can implement a RAT such asMediaFLO™, digital video broadcasting for handhelds (DVB-H), integratedservices digital broadcasting for terrestrial television broadcasting(ISDB-T), or the like. Further, the broadcast network 170 can includeone or more broadcast stations 172 that can support one-waycommunication.

The satellite positioning system 180 can be the United States GlobalPositioning System (GPS), the European Galileo system, the RussianGLONASS system, the quasi-zenith satellite system (QZSS) over Japan, theIndian Regional Navigational Satellite System (IRNSS) over India, theBeidou system over China, and/or any other suitable system. Further, thesatellite positioning system 180 can include a number of satellites 182that transmit signals for position determination.

In various embodiments, the wireless device 110 can be stationary ormobile and can also be referred to as a client device, user equipment(UE), user terminal, user device, communication device, wirelesscommunications device, handheld device, mobile device, mobile terminal,mobile station, handset, access terminal, subscriber device, subscriberterminal, subscriber station, terminal, and/or variants thereof, whichare used interchangeably to refer to any suitable mobile or stationarydevice that may operate that can communicate with a radio access network(RAN) that implements a particular radio access technology (RAT), over awired network, over a Wi-Fi network (e.g., based on IEEE 802.11, etc.),and/or with other devices via direct device-to-device (D2D) and/orpeer-to-peer (P2P) signaling protocols (e.g., LTE Direct, sometimesreferred to as LTE Advanced, AllJoyn, Wi-Fi Direct, Wi-Fi Aware,Bluetooth, Bluetooth Low Energy (BTLE), NFC, etc.). For example,according to the various aspects and embodiments described herein, thewireless device 110 may discover the other devices via the D2D and/orP2P signaling protocols according to various methods, includingtechnical specifications set forth by the 3rd Generation PartnershipProject (3GPP) (e.g., 3GPP TS 23.303, “Proximity-based services (ProSe);Stage 2), the Wi-Fi Alliance (e.g., “Wi-Fi Peer-to-Peer ServicesTechnical Specification”), etc. As such, the wireless device 110 cangenerally engage in two-way communication with the cellular system 120and/or 130, the WLAN system 140 and/or 150, devices with the WPAN system160, and/or any other suitable systems(s) and/or devices(s). Thewireless device 110 can additionally or alternatively receive signalsfrom the broadcast system 170 and/or satellite positioning system 180.In general, those skilled in the art will appreciate that the wirelessdevice 110 can communicate with any number of systems and/or networks atany given moment, which may also cause the wireless device 110 toexperience coexistence issues among various constituent radio devicesassociated therewith that may operate at the same time. Accordingly, aswill be explained in further detail herein, the wireless device 110 mayinclude a coexistence manager (CxM, not shown) having one or morefunctional modules to detect and mitigate coexistence issues.

In particular, as will be explained in further detail herein, the terms“coexistence state,” “coexistence impacts,” “coexistence parameters,”and/or variants thereof as used herein may generally represent the levelof impact, including desense (e.g., lost sensitivity due to noisesources), for the radios on a given device and may include one or moreinputs such as the operational radios, respective parameters associatedwith the operational radios such as transmit (TX) power level, operatingfrequencies, receiver sensitivities, throughput, timing, use cases, etc.Furthermore, according to various aspects, the terms “coexistencestate,” “coexistence impacts,” “coexistence parameters,” or the like asused herein may comprise secondary effects that can include temperature,process, and operational effects such as manufacturer filer variations,component aging, isolation variations (e.g., hand/object placement,channel conditions, etc.). As such, based on the above-mentionedinformation and/or other relevant factors, the impacts to one or morereceive radios can be determined. Furthermore, according to the variousaspects and embodiments described herein, the coexistence state for agiven device may be stored in a database, a lookup table, a memory,and/or any other suitable repository or data source accessible to thelocal device and represent all radios built into that device. In variousembodiments, a manufacturer associated with the device may pre-populatethe database, lookup table, memory, etc. at build time, or the database,lookup table, memory, etc. may alternatively (or additionally) becreated and/or updated during operations. Furthermore, according tovarious aspects, the coexistence state, impacts, parameters, etc. may beshared with one or more adjacent devices or other proximally locateddevices for the purposes described herein.

According to various aspects, FIG. 2 illustrates an exemplarymulti-radio wireless device that may support one or moredevice-to-device (D2D) communication technologies, according to variousaspects. Turning next to FIG. 2, a block diagram is provided thatillustrates an example design for a multi-radio wireless device 200 andmay be used as an implementation of the wireless device 110 shown inFIG. 1. As illustrated in FIG. 2, the multi-radio wireless device 200can include N radios 220 a through 220 n, which can be respectivelycoupled to N antennas 210 a through 210 n, where N can be any integervalue. Those skilled in the art will appreciate, however, that theradios 220 can be coupled to any number of antennas 210 and/or share agiven antenna 210.

In general, a radio 220 can be a unit that radiates or emits energy inan electromagnetic spectrum, receives energy in an electromagneticspectrum, or generates energy that propagates via conductive means. Byway of example, a radio 220 can be a unit that transmits a signal to asystem or a device or a unit that receives signals from a system ordevice. Accordingly, those skilled in the art will appreciate that aradio 220 can be utilized to support wireless communication. In anotherexample, a radio 220 can also be a unit (e.g., a screen on a computer, acircuit board, etc.) that emits noise, which can impact the performanceof other radios. Accordingly, those skilled in the art will furtherappreciate that a radio 220 can also be a unit that emits noise andinterference without supporting wireless communication. In variousembodiments, the respective radios 220 can support communication withone or more systems. Multiple radios 220 can additionally oralternatively be used for a given system (e.g., to transmit or receiveon different frequency bands, such as cellular and PCS bands).

In another aspect, a digital processor 230 can be coupled to radios 220a through 220 n and can perform various functions, such as processingfor data being transmitted or received via the radios 220. Theprocessing for each radio 220 can be dependent on the radio technologysupported by that radio and can include encryption, encoding,modulation, etc., for a transmitter; demodulation, decoding, decryption,etc., for a receiver, or the like. In one example, the digital processor230 can include a coexistence manager (CxM) 240 that can controloperation of the radios 220 in order to improve the performance of themulti-radio wireless device 200 as generally described herein. Thecoexistence manager 240 can have access to a database 244, which canstore information used to control the operation of the radios 220. Asexplained further below, the coexistence manager 240 can be adapted fora variety of techniques to decrease in-device interference between theradios and/or interference with one or more radios on another device inproximity to the multi-radio wireless device 200. In one example, thecoexistence manager 240 may request a measurement gap pattern or DRXcycle that allows an ISM radio to communicate during periods of LTEinactivity.

For simplicity, digital processor 230 is shown in FIG. 2 as a singleprocessor. However, those skilled in the art will appreciate that thedigital processor 230 can include any number of processors, controllers,memories, etc. In one example, a controller/processor 250 can direct theoperation of various units within the wireless device 200. Additionallyor alternatively, a memory 252 can store program codes and data for thewireless device 200. The digital processor 230, controller/processor250, and memory 252 can be implemented on one or more integratedcircuits (ICs), application specific integrated circuits (ASICs), etc.By way of a specific, non-limiting example, the digital processor 230can be implemented on a Mobile Station Modem (MSM) ASIC.

In an aspect, the coexistence manager 240 can manage operation ofrespective radios 220 utilized by multi-radio wireless device 200 inorder to avoid interference and/or other performance degradationassociated with collisions between respective radios 220 and/or with oneor more radios on another device in proximity to the multi-radiowireless device 200. The coexistence manager 240 may perform one or moreprocesses, such as those illustrated in FIG. 6 and FIG. 7, as will bedescribed in further detail below.

According to various aspects, FIG. 3 illustrates an exemplary wirelessenvironment 300 in which two wireless devices 310, 320 that are locatedin sufficient proximity to one another may negotiate a best D2D radioaccess technology (RAT) to use in establishing a D2D connection. Forexample, in various embodiments, the two wireless devices 310, 320 maynegotiate to derive a priority list that contains one or more best D2DRATs, one or more of which may be activated at a given time based on oneor more requirements, preferences, policies, and/or other suitablecriteria, as described in further detail herein.

More particularly, as shown in FIG. 3, the wireless device 310 may havea near-field communication (NFC) radio 311, a wireless wide area network(WWAN) radio 313, a wireless local area network (WLAN) radio 315, and aBluetooth radio 317 that the wireless device 310 can use to communicatewithin the wireless environment 300. For example, as depicted in FIG. 3,the wireless device 310 can wirelessly communicate with a base station340 over a WWAN link 341 using the WWAN radio 313. The wireless device310 can also wirelessly communicate with an access point 360 over a WLANlink 361 using the WLAN radio 315. Furthermore, the wireless device 310can wirelessly communicate with a Bluetooth headset 380 andBluetooth-enabled wearable device 382 over Bluetooth links 381, 383using the Bluetooth radio 317, wherein the Bluetooth headset 380 and theBluetooth-enabled wearable device 382 may be in further wirelesscommunication with each other over a Bluetooth link 384. Further still,the wireless device 310 can wirelessly communicate with one or more NFCdevices (not shown) that are within the “near field” of the wirelessdevice 310 using the NFC radio 311 via magnetic field induction.

Furthermore, in various embodiments, the wireless environment 300 mayalso include a second wireless device 320, which may likewise havemultiple radios that each operate in accordance with a different RAT.For example, as shown in FIG. 3, the second wireless device 320 may alsohave an NFC radio 321, a WWAN radio 323, a WLAN radio 325, and aBluetooth radio 327, wherein the wireless device 320 can use the radios321, 323, 325, 327 to communicate within the wireless environment 300.For example, as depicted in FIG. 3, the wireless device 320 canwirelessly communicate with a base station 344 over a WWAN link 345using the WWAN radio 323, with an access point 364 over a WLAN link 365using the WLAN radio 325, with a Bluetooth headset 385 and aBluetooth-enabled wearable device 387 over Bluetooth links 386, 388using the Bluetooth radio 327, wherein the Bluetooth headset 385 and theBluetooth-enabled wearable device 387 may be in further wirelesscommunication with each other over a Bluetooth link 389. Further still,the wireless device 320 can wirelessly communicate with one or more NFCdevices (not shown) that are within the “near field” of the wirelessdevice 320 using the NFC radio 321 via magnetic field induction.

In various embodiments, those skilled in the art will appreciate thatalthough the base stations 340, 344 are depicted as separate in FIG. 3,the wireless devices 310, 320 may in fact be in communication with thesame base station, in which case the WWAN links 341, 345 may have acommon endpoint. Analogously, those skilled in the art will appreciatethat the access points 360, 364 may correspond to a single access pointrather than separate access points as shown in FIG. 3.

Regardless of the particular arrangement, the various links that thewireless devices 310, 320 use to communicate within the wirelessenvironment 300 may cause in-device coexistence issues and/orcross-device coexistence issues. For example, as depicted at 312,in-device coexistence issues may occur at the wireless device 310 due tointerference or other coexistence impacts that may be caused when thewireless device 310 uses the WWAN radio 313, the WLAN radio 315, and theBluetooth radio 317 to communicate at substantially the same time. In asimilar respect, as depicted at 322, in-device coexistence issues mayoccur at the wireless device 320 due to interference or othercoexistence impacts that result when the wireless device 320 uses theWWAN radio 323, the WLAN radio 325, and the Bluetooth radio 327 tocommunicate at substantially the same time. Further detail relating toexample in-device coexistence impacts 312, 322 that may occur at therespective wireless devices 310, 320 will be described in further detailbelow with respect to FIG. 4. Furthermore, when the wireless devices310, 320 are within sufficient proximity, the wireless devices 310, 320,certain cross-device coexistence issues may arise, as depicted at 330.For example, if the wireless devices 310, 320 are within a range up toapproximately 500 meters, the wireless devices 310, 320 may use the WWANradios 313, 323 to form a D2D link over LTE Direct. Furthermore, if thewireless devices 310, 320 are within sufficient range to discover oneanother via the WLAN radios 315, 325, the wireless devices 310, 320 mayform a D2D link over Wi-Fi Direct. In other examples, the wirelessdevices 310, 320 may form a D2D link using the Bluetooth radios 317, 327if the wireless devices 310, 320 are within an operating range rangingfrom a few meters to a few tens of meters or using the NFC radios 311,321 if the wireless devices 310, 320 are within each other's near field(e.g., about ten centimeters or less). Further still, even if thewireless devices 310, 320 do not form a D2D link, the wirelesscommunication that occurs at the respective wireless devices 310, 320may create cross-device coexistence impacts 330 that interfere withwireless communication performed at the other wireless device (e.g., aswill be described in further detail below with respect to FIG. 5). Assuch, depending on the particular radios available and/or in use at eachwireless device 310, 320, there may be several factors to consider inchoosing the best RAT to form a D2D link between the wireless devices310, 320, including at least the in-device coexistence impacts 312, 322and the cross-device coexistence impacts 330 that such a D2D link maycause.

For example, according to various aspects, FIG. 4 illustrates variousexamples relating to the possible in-device coexistence impacts 312, 322that may occur in the wireless environment 300. More particularly, FIG.4 shows an example frequency spectrum portion 400 that comprises severalradio bands, including the industrial, scientific and medical (ISM) band410. In that context, the example in-device coexistence impacts shown inFIG. 4 may apply to a particular situation in which coupling and/orisolation between antennas on a particular wireless device is theculprit that causes the in-device coexistence impacts. Furthermore, thevarious in-device coexistence impacts and regions in the frequencyspectrum portion 400 shown in FIG. 4 apply to a particular scenario, andas such, may vary from one device to another depending on distance,filtering, device architectures, and/or other factors, as would beapparent to those skilled in the art.

As depicted in FIG. 4, the ISM radio band 410 has an 83 MHz bandwidthand covers frequencies ranging from 2400 MHz to 2483 MHz, wherein theISM band 410 may commonly be positioned between other neighboring radiobands used to operate in accordance with 3rd Generation PartnershipProject (3GPP) specifications. For example, as shown in FIG. 4, the 3GPPoperating band 40 (hereinafter the “B40 band”) 420 uses time-divisionduplexing (TDD) to operate on frequencies that range from 2300 MHz to2400 MHz. Furthermore, as shown in FIG. 4, the 3GPP operating band 7includes an uplink (UL) portion 430 (hereinafter the “B7 UL band”) thatuses frequency-division duplexing (FDD) to operate on frequenciesranging from 2500 MHz to 2570 MHz and a downlink (DL) portion 450(hereinafter the “B7 DL band”) that uses FDD to operate on frequenciesranging from 2620 MHz to 2690 MHz. In addition, between the B7 UL band430 and the B7 DL band 450, the 3GPP operating band 38 (hereinafter the“B38 band”) 440 uses TDD to operate on frequencies ranging from 2570 MHzto 2620 MHz, while the 3GPP operating band 41 (hereinafter the “B41band”) 460 uses TDD to operate on frequencies ranging from 2496 MHz to2690 MHz. However, those skilled in the art will appreciate that thefrequencies shown in FIG. 4 (and described herein) are approximations.

Accordingly, as shown in FIG. 4, the ISM band 410 is proximate to theB40 band 420, whereby there may be little to no guard band between theISM band 410 and the B40 band 420. Furthermore, the ISM band 410 is alsoproximate to the B7 UL band 430 and the B41 band 460, and the ISM band410 is less proximate to the B38 band 440 and the B7 DL band 450.However, as will be discussed in further detail below, operations in anyof the various bands 410, 420, 430, 440, 450, 460 in the frequencyspectrum portion 400 shown in FIG. 4 can potentially interfere withoperations in one or more other bands in the illustrated frequencyspectrum portion 400. As such, those skilled in the art will appreciatethat FIG. 4 merely provides exemplary interference (or coexistence)issues that can arise in the frequency spectrum portion 400 showntherein. Moreover, those skilled in the art will appreciate that FIG. 4may not provide a complete picture with respect to the potentialinterference (or coexistence) issues that may occur in the depictedfrequency spectrum portion 400 and further that operations outside thedepicted frequency spectrum portion 400 can further cause potentialinterference or coexistence issues with respect to operations that arewithin the depicted frequency spectrum portion 400 (and vice-versa).Accordingly, in-device and/or cross-device coexistence issues may ariseacross different RATs in any portion of the frequency spectrum, and thesolutions described herein to select an appropriate D2D RAT in a mannerthat may mitigate such in-device and/or cross-device coexistence issuesare generally applicable anywhere that the RAT used in a D2D connectionmay cause in-device and/or cross-device coexistence issues.

As noted above, FIG. 4 illustrates various example in-device coexistenceimpacts that may occur when the wireless devices 310, 320 shown in FIG.3 establish a D2D connection using one or more RATs that operate in theillustrated frequency spectrum portion 400, wherein the examples shownin FIG. 4 may generally comprise in-device coexistence impacts betweenoperations within the ISM band 410 and LTE operations outside the ISMband 410. However, as further mentioned above, the example in-devicecoexistence impacts and regions in the frequency spectrum portion 400shown in FIG. 4 apply to a particular scenario, and as such, may varyfrom one device to another depending on distance, filtering, devicearchitectures, and/or other factors. For example, the desensing depictedin FIG. 4 at 412, 414, 426, 428, etc. represents best-case results withhigh-performance a thin-film bulk acoustic resonator (FBAR) filter.Accordingly, in a device that uses a more typical and relatively cheapersurface acoustic wave (SAW) filter, entire portions of bands may berendered inoperable, including the operations shown at 422, 432, 424,416, 418 in addition to the desensing depicted at 412, 414, 426, 428where high-performance FBAR filters are used. Furthermore, although theresults shown in FIG. 4 represent example in-device coexistence impactswhere the various RATs are designed for coexistence such thathigh-performance filters are used, the results could be much worse whenencountering a cross-device victim/aggressor scenario where higher costfilters were not used in anticipation of possible coexistence problems.Further still, the results shown in FIG. 4 may depend on transmit power,receiver sensitivity, etc., and filters may also have performancevariations due to temperature and process variation, furthercomplicating coexistence mitigation efforts. As such, those skilled inthe art will appreciate that any particular values referred to hereinand any particular in-device and/or cross-device coexistence impactsdescribed herein are merely illustrative with respect to the particularscenarios depicted and described, as there will be many differentfactors that can cause in-device and/or cross-device coexistence impactsbetween two wireless devices seeking to establish a D2D connection.

For example, in the particular scenario shown in FIG. 4, LTE operations432 that are conducted in the B7 UL band 430 and use the closest channelto the ISM band 410 (e.g., the lowest 10 MHz in the B7 UL band) cancause in-device coexistence impacts whereby Bluetooth and/or WLANoperations may be desensed across the ISM band 410, as depicted at 412(e.g., the LTE operations 432 in the B7 UL band 430 may desense WLANchannel 11 by ˜30 decibels (dB), wherein the desensing shown at 412 canbe more or less than 30 dB depending on circumstances). In anotherexample, LTE operations that use the top 30 MHz in the B40 band 420, asdepicted at 422, can cause in-device coexistence impacts wherebyBluetooth and/or WLAN operations may be desensed across the ISM band410, as further depicted at 412. However, LTE operations in the bottom70 MHz in the B40 band 420, as depicted at 424, may cause a smallerin-device coexistence impact, whereby desensing may only be experiencedin the lower 20 MHz in the ISM band 410, as depicted at 414.Furthermore, Bluetooth and/or WLAN operations within the ISM band 410can cause coexistence impacts outside the ISM band 410. For example,Bluetooth and/or WLAN operations that use the lower 20 MHz in the ISMband 410, as depicted at 416, can cause an in-device coexistence impactin that LTE operations may be desensed across the entire B40 band 420,as depicted at 426. However, Bluetooth and/or WLAN operations conductedabove ˜2420 MHz, as depicted at 418, may cause a relatively smallerin-device coexistence impact, whereby desensing may only be experiencedin the upper 30 MHz in the B40 band 420, as depicted at 428. Again, asmentioned above, those skilled in the art will appreciate that thein-device coexistence impacts shown in FIG. 4 and the degree to whichsuch in-device coexistence impacts may cause desensing due to operationsin different RATs may vary based on many factors, which may includefilter parameters, transmit power, and receiver sensitivity levels,among many other factors.

Furthermore, referring now to FIG. 5, illustrates example cross-devicecoexistence impacts that may occur in the wireless environment 300 shownin FIG. 3. More particularly, the graph depicted at 510 may generallyillustrate cross-device coexistence impacts where LTE operations that afirst wireless device (e.g., wireless device 310) conducts in a releasedspectrum portion 512 within the B40 band may cause interference and/ordesensing at a second wireless device (e.g., wireless device 320)conducting Wi-Fi operations in the ISM band 516, wherein the exampleshown at 510 may assume a 10 MHz guard band 514 between the ISM band 516and the released spectrum portion 512 in the B40 band, wherein thereleased spectrum portion 512 may typically extend all the way down to2300 MHz and all the way up to 2400 MHz (e.g., without the guard band514). Accordingly, in the illustrated example that assumes the 10 MHzguard band 514 between the ISM band 516 and the released spectrumportion 512 in the B40 band, the first wireless device may conduct theLTE operations in the released spectrum portion 512 in the B40 bandbetween ˜2300 MHz to 2390 MHz. Furthermore, in the example illustratedin FIG. 5, the measured channels in the B40 band generally range from˜2360 MHz to ˜2400 MHz because experimental results and analysis did notreveal significant problems in the lower channels in the B40 band, ascan be extrapolated from the cross-device coexistence impacts shown inFIG. 5. Accordingly, in the following description, the first wirelessdevice conducting the LTE operations in the released spectrum portion512 within the B40 band may be referred to as an “LTE 23 dBm aggressor”and the second wireless device that conducts the Wi-Fi operations in theISM band 516 and may experience potential interference/desensingcross-device coexistence impacts from the LTE 23 dBm aggressor may bereferred to as a “Wi-Fi victim.”

As shown in the graph depicted at 510, an interference level 518 thatthe Wi-Fi victim experiences due to the operations that the LTE 23 dBmaggressor conducts on any particular channel within the depictedreleased spectrum portion 512 within the B40 band may vary depending ona distance 520 from the LTE 23 dBm aggressor to the Wi-Fi victim,wherein the interference level 518 that the Wi-Fi victim experiences maygenerally increase as the distance 520 from the LTE 23 dBm aggressor tothe Wi-Fi victim decreases. Furthermore, a desensitization level 522experienced at the Wi-Fi victim may generally increase as the releasedspectrum portion 512 that the LTE 23 dBm aggressor uses to conduct theLTE operations approaches the guard band between the released spectrumportion 512 in the B40 band and the ISM band 516. Accordingly, asdepicted at 524, the Wi-Fi victim may experience increasing desense asthe distance 520 from the LTE 23 dBm aggressor to the Wi-Fi victimdecreases, and may experience further increased desense as the LTEoperations associated with the LTE 23 dBm aggressor are conducted athigher frequencies within the released spectrum portion 512 within theB40 band.

However, those skilled in the art will appreciate that the cross-devicecoexistence impacts that may result from different wireless devicesconducting operations in various frequency bands and/or using variousRATs may vary depending on various factors. For example, the graphdepicted at 530 generally illustrates cross-device coexistence impactswhere another wireless device (“Device B”) having a different WLANreceiver experiences desensitization from a 5 MHz wide TDD LTEinterferer at a ˜20 meter distance. In particular, the graph shown at530 may depict experimental results in which the vertical axisrepresents increasing desensitization levels at Device B, wherein thedesensitization levels may vary depending on a center frequency offsetfrom a low band edge in the ISM band 516 and a distance from the TDD LTEinterferer to Device B. For example, as depicted at 532, Device B maystart to experience a desensitization level over ˜10 dB where the TDDLTE interferer uses a 2.5 MHz center frequency offset from the low bandedge in the ISM band 516 and a distance 536 from Device B to the TDD LTEinterferer is ˜22 meters. Furthermore, at a ˜6 meter distance from theTDD LTE interferer, Device B may start to experience a desensitizationlevel over ˜10 dB where the TDD LTE interferer uses a ˜30.0 MHz centerfrequency offset from the low band edge in the ISM band 516, adesensitization level over ˜30 dB where the TDD LTE interferer uses a˜15.0 MHz center frequency offset from the low band edge in the ISM band516, and so on.

Accordingly, referring again to FIG. 3, the following descriptionprovides various solutions that may be used to identify a best RAT touse in establishing the D2D connection due to the possibility that thewireless devices 310, 320 may each support one or several RATs that canbe used to establish a D2D connection. As such, depending on the radioconfiguration associated with the wireless devices 310, 320 and theavailable RAT options that can be used to establish the D2D connection,the solutions described herein may involve a negotiation between thewireless devices 310, 320 to select the best RAT and/or multi-radioparameters to use when establishing the D2D connection based on one ormore criteria that may relate to performance, power, in-devicecoexistence impacts, cross-device coexistence impacts, and/orpreferences (e.g., user preferences, device preferences, operatorpreferences, etc.). For example, in certain use cases, a particular RATmay not be available or optimal with respect to a particular D2Dconnection even though both wireless devices 310, 320 may support theparticular RAT (e.g., where the wireless devices 310, 320 are associatedwith different manufacturers that implement the RAT in different ways,where one RAT may be unable to provide sufficient performance withrespect to the requirements associated with a particular application orsession, where using a particular RAT may cause in-device and/orcross-device coexistence impacts, etc.). As such, in variousembodiments, the wireless devices 310, 320 may each have a respectivecoexistence manager 318, 328 in addition to a respective policy database319, 329, wherein the wireless devices 310, 320 may run a D2Dcoexistence protocol to mutually negotiate the “best” RAT to use inestablishing a D2D connection.

In various embodiments, the wireless devices 310, 320 may therefore runthe D2D coexistence protocol to learn a radio configuration and radiocapabilities associated with one another and thereby identify one ormore “compatible” RATs that can be used to establish the D2D connection,wherein the term “compatible” as used herein may refer to the ability toestablish a D2D connection according to the local version(s) of the D2DRATs that are implemented on the respective wireless devices 310, 320(i.e., the term “compatible” as used herein means more than the mereability to establish a connection according to an established standardsuch as Wi-Fi). For example, where the wireless devices 310, 320correspond to smartphones from different manufacturers that implementdifferent Wi-Fi Direct versions, the “compatible” D2D RATs may notinclude Wi-Fi Direct in the event that the wireless devices 310, 320cannot communicate using respective local Wi-Fi Direct versions eventhough both wireless devices 310, 320 support Wi-Fi Direct as a possibleD2D RAT. Accordingly, in various embodiments, the wireless devices 310,320 may exchange the radio configuration and radio capabilitiesassociated with one another to learn the compatible D2D RATs that can beused to establish the D2D connection (i.e., the possible RATs that thewireless devices 310, 320 can use to establish the D2D connection usinglocally implemented versions on the respective wireless devices 310,320) and further to learn a multi-radio coexistence state associatedwith each other. For example, in various embodiments, the multi-radiocoexistence state exchanged between the wireless devices 310, 320 maycomprise in-device coexistence impacts and/or cross-device coexistenceimpacts measured at each respective wireless device 310, 320).

In various embodiments, the wireless devices 310, 320 may then mutuallynegotiate the best RAT to establish the D2D connection based on thecompatible D2D RATs and the multi-radio coexistence state(s) exchangedaccording to the D2D coexistence protocol. For example, in variousembodiments, the wireless device 310 may attempt to engage D2Dcommunications with the wireless device 320 according to each locallysupported D2D RAT (e.g., the wireless device 310 may attempt to engageNFC connectivity via the NFC radio 311, LTE Direct connectivity via theWWAN radio 313, Wi-Fi Direct connectivity via the WLAN radio 315,Bluetooth connectivity via the Bluetooth radio 317, etc.). As such, ifthe wireless device 310 determines that all locally supported D2D RATsfailed to achieve connectivity, the D2D coexistence protocol may failwithout establishing a D2D connection with the wireless device 320.However, if the wireless device 310 determines that one or more locallysupported D2D RATs successfully achieved connectivity such that thereare one or more compatible D2D RATs, the wireless devices 310, 320 maythen negotiate one or more best D2D RATs to use in establishing the D2Dconnection. For example, in the simplest use case, only one D2D RAT maybe successful in achieving connectivity between the wireless devices310, 320, whereby the wireless devices 310, 320 may establish a D2Dconnection according to that D2D RAT.

However, where multiple D2D RATs succeeded in achieving connectivity,the wireless devices 310, 320 may mutually negotiate or otherwise selectone or more best D2D RATs according to one or more criteria that relateto performance, power, in-device coexistence impacts, cross-devicecoexistence impacts, preferences, policies, and/or other suitablefactors. For example, where the multiple D2D RATs that successfullyachieved connectivity comprise Bluetooth and LTE Direct, the wirelessdevices 310, 320 may select Bluetooth, LTE Direct, or both depending oncriteria that relate to performance metrics (e.g., use Bluetooth if theD2D connection is established to transfer a file having a small size,use LTE Direct if the D2D connection is established to transfer a largefile because LTE Direct offers faster transfer speeds than Bluetooth,use both if the wireless devices 310, 320 are more than a few metersapart such that the LTE Direct connection can take over in the eventthat the Bluetooth connection between the wireless devices 310, 320 islost, etc.). In another example, the wireless devices 310, 320 mayselect one or more best D2D RATs to minimize power consumption, whichmay comprise selecting the fastest D2D link (e.g., preferring Wi-FiDirect over LTE Direct) under the “race-to-idle” principle in whichtransmissions are conducted as quickly as possible before returning theradios to an inactive idle state. In another scenario, one D2D RAT mayconsume significantly more active power than another such that the morepower-hungry D2D RAT may simply not be considered at a high priority(e.g., Wi-Fi and/or LTE radios typically use more power than Bluetoothand/or NFC). More generally, in scenarios where the optimization metricpertains to selecting a high-performance interface (e.g., to transfer alarge file, conduct a D2D session that involves a service with latencyor other quality of service constraints, etc.), both the “race-to-idle”and “active power consumption” factors may be considered when selectingthe one or more best D2D RATs. However, where a small file is to betransferred or the context otherwise does not require a high-performanceinterface, then Bluetooth and/or BTLE may simply be considered the bestD2D RAT, unless there are potential in-device and/or cross-devicecoexistence impacts and/or other considerations that may make Bluetoothand/or BTLE undesirable (e.g., not concurrently participating in otherlinks such as to a wireless headset or wireless speakers).

In still other examples, operator policies may be considered, whereinoperator policies may generally exist at least when one or more LTEchannels are selected for D2D communications, as opposed to Wi-Fi. Assuch, if the operator associated with either or both wireless devices310, 320 determines that using a given spectrum in a particular area maynot be enabled for some reason, the operator may disable LTE Direct inthe policy database 319, 329 associated with the applicable wirelessdevice(s) 310, 320 (e.g., where the wireless device(s) 310, 320 have notpaid a fee to enable LTE Direct, where given spectrum channels arepotentially limited to help alleviate network or other conditions in alocal area). Furthermore, similar issues may arise in use cases thatinvolve operator-controlled Wi-Fi, which may come with similar access orsubscription-based use such that Wi-Fi may be disabled as a possible D2DRAT in a given region. In another example where an operator policy maybe considered in negotiating the best D2D RAT(s), a particular operatormay prefer that the wireless devices 310, 320 communicate over LTEDirect and/or using operator-controlled Wi-Fi to monetize airtime overfree Wi-Fi and/or other free D2D RATs or vice versa (e.g., where thecellular network and/or the operator-controlled Wi-Fi network is atcapacity and other D2D RATs are therefore preferred).

Furthermore, according to various embodiments, the wireless devices 310,320 may further mutually negotiate certain modified radio parameterswhere the “best” D2D RAT mutually negotiated between the wirelessdevices 310, 320 has the potential to cause in-device and/orcross-device coexistence impacts. In particular, the wireless devices310, 320 may mutually negotiate the modified radio parameters in aneffort to eliminate, reduce, or at least mitigate the potentialin-device and/or cross-device coexistence impacts and the wirelessdevices 310, 320 may then attempt to establish the D2D connectionaccording to the best D2D RAT if the modified radio parameterssufficiently eliminate, reduce, or otherwise mitigate the potentialin-device and/or cross-device coexistence impacts. Alternatively, wherethe modified radio parameters do not sufficiently reduce the in-deviceand/or cross-device coexistence impacts, the wireless devices 310, 320may attempt one or more next best D2D RATs until the in-device and/orcross-device coexistence impacts has been sufficiently reduced and thenestablish the D2D connection according to the multi-radio configurationthat provides the best in-device and cross-device coexistence operatingparameters. Accordingly, as will be described in further detail belowwith respect to FIG. 6 and FIG. 7, the following table illustratesvarious example scenarios in which the wireless devices 310, 320 maymutually negotiate and select a D2D RAT.

TABLE 1 D2D Link Selection Scenarios D2D RAT Problem D2D Link OptionsMetric Selection Incompatible RAT One (e.g., Small File LTE Direct(e.g., Wi-Fi Direct) LTE Direct) Size Incompatible RAT Multiple (e.g.,Small File Bluetooth (e.g., Wi-Fi Direct) Bluetooth Size and LTE Direct)Incompatible RAT Multiple (e.g., Large File LTE Direct (e.g., Wi-FiDirect) Bluetooth Size and LTE Direct) In-Device Multiple (e.g., NotBest Coexistence Coexistence NFC, Bluetooth, Specified Performance Wi-FiDirect, and LTE Direct) Cross-Device Multiple (e.g., Not BestCoexistence Coexistence NFC, Bluetooth, Specified Performance Wi-FiDirect, and LTE Direct)According to various aspects, FIG. 6 illustrates an example methodology600 to negotiate a best RAT to use in establishing a D2D connectionbetween two peer devices. In particular, at block 610, a first wirelessdevice may determine one or more locally available device-to-device(D2D) RATs. For example, the first wireless device may support D2D RATsthat include NFC, Bluetooth, Wi-Fi Direct, and LTE Direct, althoughWi-Fi Direct may be excluded from the locally available D2D RATs in theevent that the first wireless device determines that a Wi-Fi radio hasbeen turned off. Accordingly, the locally available D2D RATs that aredetermined at block 610 may generally depend on the D2D RATs that aresupported on the first wireless device in addition to any applicableuser, device, and/or operator preferences (e.g., a user may define apreference to avoid using LTE Direct when other D2D RATs are possible toavoid incurring data charges).

In various embodiments, at block 620, the first wireless device may thenengage the target D2D peer device via the locally available D2D RAT(s)and then determine whether at least one locally available D2D RATsuccessfully achieved connectivity with the target D2D peer device atblock 630. For example, in various embodiments, the first wirelessdevice may engage the target D2D peer device via each locally availableD2D RAT, which may be done consecutively or in parallel (e.g., dependingon an original equipment manufacturer (OEM) configuration, apolicy-based configuration, and/or other suitable criteria).Alternatively, in various embodiments, the first wireless device mayderive a priority list that orders the locally available D2D RATsaccording to policy, priority, and/or other criteria. In such a usecase, at block 620, the first wireless device may sequentially attemptto engage the target D2D peer device via the locally available D2D RATsaccording to the ordered priority list and then stop at the first D2DRAT in the ordered priority list that succeeds in achieving connectivitywith the target D2D peer device at block 632. For example, in eithercase, the first wireless device and the target D2D peer device may eachsupport Wi-Fi Direct and LTE Direct, but Wi-Fi Direct may nonethelessfail to successfully achieve connectivity in certain use cases due toproprietary limitations (e.g., when the first wireless device and thetarget D2D peer device are associated with different manufacturers). Assuch, in response to determining that connectivity with the target D2Dpeer device could not be achieved at block 630, the D2D linkestablishment between the first wireless device and the target D2D peerdevice may fail at block 634. Alternatively, if at least one locallyavailable D2D RAT successfully achieved connectivity with the target D2Dpeer device, the potential D2D peer devices may then determine whetherone or multiple D2D link options are available at block 640. Forexample, where Wi-Fi Direct failed to achieve connectivity (e.g., due toproprietary limitations) and NFC and Bluetooth also failed to achieveconnectivity (e.g., due to the first wireless device and the target D2Dpeer device not being within sufficient proximity) but LTE Directsuccessfully achieved connectivity, the potential D2D peer devices maydiscover at block 640 that the mobile network operator (MNO) controlledLTE Direct standard is the only available D2D link option.

Accordingly, in response to discovering at block 640 that only one D2DRAT successfully achieved connectivity, the first wireless device andthe target D2D peer device may then establish a D2D link at block 650via the only available compatible D2D RAT. Alternatively, in response todiscovering at block 640 that multiple D2D RATs successfully achievedconnectivity, the first wireless device and the target D2D peer devicemay then negotiate a compatible D2D RAT at block 645 prior toestablishing the D2D link via the negotiated compatible D2D RAT at block650. For example, in response to determining at block 640 that Bluetoothand LTE Direct successfully achieved connectivity, the first wirelessdevice may suggest a Bluetooth link at block 645 if the D2D link isestablished to transfer a file having a small size or alternativelysuggest an LTE Direct link at block 645 if the D2D link is establishedto transfer a file having a large size. In other examples, as will bedescribed in further detail below with respect to FIG. 7, thenegotiation conducted at block 645 may be used to select a compatibleRAT that may best mitigate in-device and/or cross-device coexistenceissues. In any case, once the potential D2D peer devices negotiate thecompatible D2D RAT at block 645, the first wireless device and thetarget D2D peer device may then establish the D2D link at block 650 viathe negotiated compatible D2D RAT and exchange data over the establishedD2D link.

According to various aspects, FIG. 7 illustrates another examplemethodology 700 to negotiate a best RAT to use in establishing a D2Dconnection between two peer devices in a manner that may mitigatein-device and cross-device coexistence impacts, wherein the methodology700 shown in FIG. 7 may generally correspond to one example negotiationthat may occur at block 645 as shown in FIG. 6. In the followingdescription, the two peer devices may be assumed to comprise a firstwireless device that comprises a WLAN radio conducting Wi-Fi operationsat 2.4 GHz on channel 6 to a first access point, a Bluetooth radioconducting Bluetooth operations, and a WWAN radio conducting LTEoperations in the B40 band in addition to a second wireless device thatcomprises a WLAN radio conducting Wi-Fi operations at 2.4 GHz on channel1 to a second access point, a Bluetooth radio conducting Bluetoothoperations, and a WWAN radio conducting 3G cellular operations. In thatcontext, the 2.4 GHz that the first wireless device and the secondwireless device use to conduct the respective Wi-Fi operations maygenerally be divided into 14 channels that are spaced 5 MHz apart,starting at channel 1 centered at 2.412 GHz. Accordingly, the firstwireless device conducting 2.4 GHz Wi-Fi operations on channel 6 mayoperate at a 2.437 GHz center frequency, while the second wirelessdevice conducting 2.4 GHz Wi-Fi operations on channel 1 may operate at a2.412 GHz center frequency, and the first wireless device and the secondwireless device may each have multi-radio coexistence parameters chosento optimize local operations.

In various embodiments, at block 710, the first wireless device and thesecond wireless device may each run a D2D coexistence protocol, whichmay comprise initially selecting a compatible D2D RAT at block 720. Thefirst and second wireless devices may then conduct service discovery toexchange device coexistence states and mutually determine a bestconfiguration associated with the current D2D RAT at block 730. Forexample, assuming that the initially selected D2D RAT is Wi-Fi Direct,the first and second wireless devices may mutually determine that Wi-Fiat 5 GHz is best (e.g., because the 5 GHz band may alleviate thecoexistence problems due to being comparatively far away from otherradios). In that context, various IEEE 802.11 standards addmultiple-input multiple-output (MIMO) antenna support to operate on boththe 2.4 GHz band and the lesser-used 5 GHz band that can operate athigher maximum data rates, wherein the dual-band feature may or may notbe supported on certain devices. As such, in the above-mentioned examplewhere the first and second wireless devices mutually determine thatWi-Fi at 5 GHz is best, the service discovery conducted between thefirst and second wireless devices may reveal that both wireless devicessupport the dual-band feature that allows the wireless devices toconduct Wi-Fi operations in the 5 GHz band. Accordingly, in variousembodiments, the first and second wireless devices may determine whetherthe best D2D RAT configuration is available at block 740, which maydepend on whether both devices can support the best D2D RATconfiguration, whether the best D2D RAT configuration causes in-deviceand/or cross-device coexistence impacts at either wireless device,and/or other factors. In various embodiments, in response to the firstand second wireless devices determining that the best D2D RATconfiguration is available, the first and second wireless devices maythen select the current D2D RAT and establish a D2D connection accordingto the best configuration associated therewith at block 745.

Alternatively, in response to the first and second wireless devicesdetermining that the best D2D RAT configuration is not available (e.g.,where the wireless devices are forced to use 2.4 GHz Wi-Fi because 5 GHzWi-Fi is unsupported), the first and second wireless devices may thenmutually determine a modified configuration associated with the currentD2D RAT to best mitigate in-device and/or cross-device coexistenceimpacts and adjust respective multi-radio configurations associatedtherewith accordingly at block 750. For example, the modifiedconfiguration may comprise a mutual determination that the best modifiedconfiguration is to (i) select Wi-Fi channel 11 causes the leastin-device and/or cross-device coexistence impact on the LTE operationsthat the first wireless device conducts in the B40 band, (ii) instructthe first wireless device to reduce transmit power to back off Wi-Fitransmit power to the second wireless device by a certain number ofdecibels (dB), and (iii) instruct a Bluetooth radio to adjust AdaptiveFrequency Hopping (AFH) patterns accordingly. In various embodiments,the first and second wireless devices may then determine whether themodified (adjusted) multi-radio configuration sufficiently mitigates anyin-device and/or cross-device coexistence impacts on the current D2DRAT, in which case the first and second wireless devices may then selectthe current D2D RAT and establish a D2D connection according to themodified multi-radio configuration at block 765. Otherwise, if themodified multi-radio configuration does not sufficiently mitigate thein-device and/or cross-device coexistence impacts on the current D2DRAT, the first and second wireless devices may determine whether anyfurther compatible D2D link options are available at block 770. In theaffirmative, the methodology 700 may return to block 720 and the firstand second wireless devices may attempt to establish a D2D connection onthe next compatible D2D RAT in a substantially similar manner to thatdescribed above until a D2D RAT that sufficiently satisfies performanceand in-device and cross-device coexistence requirements has been met, orin the alternative, the compatible D2D RAT negotiation may fail at block780 if the first and second wireless devices exhaust all compatible D2DRAT options without finding at least one compatible D2D RAT thatsufficiently satisfies performance and in-device and cross-devicecoexistence requirements.

According to various aspects, FIG. 8 illustrates a block diagram thatmay correspond to two peer devices that may engage in D2Dcommunications. In the following description, FIG. 8 will be explainedin a context where a first peer device 810 transmits data to a secondpeer device 850 over a D2D connection and the second peer device 850receives the data transmitted from the first peer device 810 over theD2D connection. However, those skilled in the art will appreciate thatthe transmit and receive functions may also be reversed, in that thesecond peer device 850 can transmit data to the first peer device 810over the D2D connection and the first peer device 810 can receive datatransmitted from the second peer device 850 over the D2D connection insubstantially the same manner. Accordingly, in the example shown in FIG.8, both the first peer device 810 and the second peer device 850 mayhave a transceiver that includes a transmitter system and a receiversystem. At the first peer device 810, traffic data for a number of datastreams is provided from a data source 812 to a transmit (TX) dataprocessor 814.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, wherein N_(S) is less than or equal to min{N_(T), N_(R)}. Eachof the N_(S) independent channels corresponds to a dimension. The MIMOsystem can provide improved performance (e.g., higher throughput and/orgreater reliability) if the additional dimensionalities created by themultiple transmit and receive antennas are utilized.

A MIMO system supports time division duplex (TDD) and frequency divisionduplex (FDD) systems. In a TDD system, the uplink and downlinktransmissions are on the same frequency region so that the reciprocityprinciple allows the estimation of the downlink channel from the uplinkchannel. This enables the transmitting peer device to extract transmitbeamforming gain on the downlink when multiple antennas are available atthe transmitting peer device. In one aspect, each data stream istransmitted over a respective transmit antenna. The TX data processor814 formats, codes, and interleaves the traffic data for each datastream based on a particular coding scheme selected for that data streamto provide coded data. The coded data for each data stream can bemultiplexed with pilot data using OFDM techniques. The pilot data is aknown data pattern processed in a known manner and can be used at thereceiver system to estimate the channel response. The multiplexed pilotand coded data for each data stream is then modulated (e.g., symbolmapped) based on a particular modulation scheme (e.g., BPSK, QPSK,M-PSK, or M-QAM) selected for that data stream to provide modulationsymbols. The data rate, coding, and modulation for each data stream canbe determined by instructions performed by a processor 830 operatingwith a memory 832.

The modulation symbols for respective data streams are then provided toa TX MIMO processor 820, which can further process the modulationsymbols (e.g., for OFDM). The TX MIMO processor 820 then provides N_(T)modulation symbol streams to N_(T) transmitters (TMTR) 822 a through 822t. In certain aspects, the TX MIMO processor 820 applies beamformingweights to the symbols of the data streams and to the antenna from whichthe symbol is being transmitted.

Each transmitter 822 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from the transmitters 822 a through 822 t are thentransmitted from N_(T) antennas 824 a through 824 t, respectively.

At the receiving peer device 850, the transmitted modulated signals arereceived by N_(R) antennas 852 a through 852 r and the received signalfrom each antenna 852 is provided to a respective receiver (RCVR) 854 athrough 854 r. Each receiver 854 conditions (e.g., filters, amplifies,and downconverts) a respective received signal, digitizes theconditioned signal to provide samples, and further processes the samplesto provide a corresponding “received” symbol stream. An RX dataprocessor 860 then receives and processes the N_(R) received symbolstreams from N_(R) receivers 854 based on a particular receiverprocessing technique to provide N_(R) “detected” symbol streams. The RXdata processor 860 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by the RX data processor 860 is complementary to theprocessing performed by the TX MIMO processor 820 and the TX dataprocessor 814 at the first peer device 810.

A processor 870 (operating with a memory 872) periodically determineswhich pre-coding matrix to use (discussed below). The processor 870formulates an uplink message having a matrix index portion and a rankvalue portion.

The uplink message can include various types of information regardingthe communication link and/or the received data stream. The uplinkmessage is then processed by a TX data processor 838, which alsoreceives traffic data for a number of data streams from a data source836, modulated by a modulator 880, conditioned by transmitters 854 athrough 854 r, and transmitted back to the first peer device 810. At thefirst peer device 810, the modulated signals from the receiver system850 are received by antennas 824, conditioned by receivers 822,demodulated by a demodulator 840, and processed by an RX data processor842 to extract the uplink message transmitted by the receiver system850. The processor 830 then determines which pre-coding matrix to usefor determining the beamforming weights, then processes the extractedmessage

Those skilled in the art will appreciate that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Further, those skilled in the art will appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the aspects disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted to departfrom the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration).

The methods, sequences and/or algorithms described in connection withthe aspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM, flash memory, ROM, EPROM, EEPROM,registers, hard disk, a removable disk, a CD-ROM, or any other form ofstorage medium known in the art. An exemplary storage medium is coupledto the processor such that the processor can read information from, andwrite information to, the storage medium. In the alternative, thestorage medium may be integral to the processor. The processor and thestorage medium may reside in an ASIC. The ASIC may reside in a wirelessdevice (e.g., an IoT device). In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

In one or more exemplary aspects, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave, then the coaxial cable, fiber optic cable, twisted pair, DSL,or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes CD, laser disc, optical disc, DVD, floppy disk and Blu-ray discwhere disks usually reproduce data magnetically and/or optically withlasers. Combinations of the above should also be included within thescope of computer-readable media.

While the foregoing disclosure shows illustrative aspects of thedisclosure, it should be noted that various changes and modificationscould be made herein without departing from the scope of the disclosureas defined by the appended claims. The functions, steps and/or actionsof the method claims in accordance with the aspects of the disclosuredescribed herein need not be performed in any particular order.Furthermore, although elements of the disclosure may be described orclaimed in the singular, the plural is contemplated unless limitation tothe singular is explicitly stated.

What is claimed is:
 1. A method for selecting a radio access technology(RAT) to use in a device-to-device (D2D) connection, comprising:requesting, by a first wireless device, a radio configuration from asecond wireless device, wherein the requested radio configurationcomprises a coexistence state and one or more radio capabilitiesassociated with the second wireless device; receiving, at the firstwireless device, the coexistence state and the one or more radiocapabilities from the second wireless device; negotiating one or morecompatible RATs available to use in a D2D connection between the firstwireless and the second wireless device according to at least thecoexistence state and the one or more radio capabilities received fromthe second wireless device, wherein the negotiating comprises exchangingin-device and cross-device coexistence states between the first wirelessdevice and the second wireless device; and establishing one or more D2Dconnections between the first wireless device and the second wirelessdevice using the negotiated one or more compatible RATs.
 2. The methodrecited in claim 1, wherein negotiating the one or more compatible RATsfurther comprises: determining that at least one of the compatible RATscauses in-device interference at one or more of the first wirelessdevice or the second wireless device based on the exchanged in-deviceand cross-device coexistence states; negotiating a modifiedconfiguration associated with the at least one compatible RAT tomitigate the in-device interference; and adjusting a multi-radioconfiguration at the first wireless device according to the negotiatedmodified configuration associated with the at least one compatible RAT.3. The method recited in claim 2, wherein the second wireless device isconfigured to adjust the radio configuration associated therewithaccording to the modified configuration.
 4. The method recited in claim1, wherein negotiating the one or more compatible RATs furthercomprises: determining that at least one of the compatible RATs causescross-device interference at one or more of the first wireless device orthe second wireless device based on the exchanged in-device andcross-device coexistence states; and negotiating a modifiedconfiguration associated with the at least one compatible RAT tomitigate the cross-device interference; and adjusting a multi-radioconfiguration at the first wireless device according to the negotiatedmodified configuration associated with the at least one compatible RAT.5. The method recited in claim 4, wherein the second wireless device isconfigured to adjust the radio configuration associated therewithaccording to the modified configuration.
 6. The method recited in claim1, wherein negotiating the one or more compatible RATs furthercomprises: determining that one compatible RAT is available to use inthe D2D connection between the first wireless and the second wirelessdevice, wherein the one or more D2D connections between the firstwireless device and the second wireless device comprise one D2Dconnection established according to the one compatible RAT.
 7. Themethod recited in claim 1, wherein negotiating the one or morecompatible RATs further comprises: determining that multiple compatibleRATs are available to use in the D2D connection between the firstwireless and the second wireless device; and selecting one or more ofthe multiple compatible RATs to meet a performance requirementassociated with the D2D connection.
 8. The method recited in claim 7,further comprising: deriving a priority list that orders the multiplecompatible RATs according to one or more policies that are based on oneor more of a user preference, a device state, or a mobile networkoperator preference, wherein the one or more of the multiple compatibleRATs are further selected according to the derived priority list.
 9. Themethod recited in claim 1, wherein the one or more compatible RATs arenegotiated according to one or more policies that are based on one ormore of a user preference, a device state, or a mobile network operatorpreference.
 10. The method recited in claim 1, wherein the one or morecompatible RATs comprise one or more of LTE Direct, Wi-Fi Direct,Bluetooth, or Near Field Communication.
 11. A wireless device,comprising: multiple radios that each support a different radio accesstechnology (RAT); a transmitter configured to transmit a request to atarget peer wireless device; a receiver configured to receive acoexistence state and one or more radio capabilities associated with thetarget peer wireless device in response to the transmitted request; andone or more processors configured to: exchange in-device andcross-device coexistence states between the wireless device and thetarget peer wireless device; negotiate one or more compatible RATsavailable to use in a device-to-device (D2D) connection between thewireless and the target peer wireless device according to the exchangedin-device and cross-device coexistence states; and establish one or moreD2D connections between the wireless device and the target peer wirelessdevice using the negotiated one or more compatible RATs.
 12. Thewireless device recited in claim 11, wherein the one or more processorsare further configured to: determine that at least one of the compatibleRATs causes in-device interference at one or more of the wireless deviceor the target peer wireless device based on the exchanged in-device andcross-device coexistence states; negotiate a modified configurationassociated with the at least one compatible RAT to mitigate thein-device interference; and adjust a multi-radio configuration at thewireless device according to the negotiated modified configurationassociated with the at least one compatible RAT.
 13. The wireless devicerecited in claim 12, wherein the target peer wireless device is furtherconfigured to adjust the radio configuration associated therewithaccording to the modified configuration.
 14. The wireless device recitedin claim 11, wherein the one or more processors are further configuredto: determine that at least one of the compatible RATs causescross-device interference at one or more of the wireless device or thetarget peer wireless device based on the exchanged in-device andcross-device coexistence states; and negotiate a modified configurationassociated with the at least one compatible RAT to mitigate thecross-device interference; and adjust a multi-radio configuration at thewireless device according to the negotiated modified configurationassociated with the at least one compatible RAT.
 15. The wireless devicerecited in claim 14, wherein the target peer wireless device is furtherconfigured to adjust the radio configuration associated therewithaccording to the modified configuration.
 16. The wireless device recitedin claim 11, wherein the one or more processors are further configuredto: determine that one compatible RAT is available to use in the D2Dconnection between the wireless and the target peer wireless device,wherein the one or more D2D connections between the wireless device andthe target peer wireless device comprise one D2D connection establishedaccording to the one compatible RAT.
 17. The wireless device recited inclaim 11, wherein the one or more processors are further configured to:determine that multiple compatible RATs are available to use in the D2Dconnection between the wireless and the target peer wireless device; andselect one or more of the multiple compatible RATs to meet a performancerequirement associated with the D2D connection.
 18. The wireless devicerecited in claim 17, wherein the one or more processors are furtherconfigured to: derive a priority list that orders the multiplecompatible RATs according to one or more policies that are based on oneor more of a user preference, a device state, or a mobile networkoperator preference and select the one or more of the multiplecompatible RATs according to the derived priority list.
 19. Anapparatus, comprising: means for requesting a radio configuration from atarget peer wireless device, wherein the requested radio configurationcomprises a coexistence state and one or more radio capabilitiesassociated with the target peer wireless device; means for receiving thecoexistence state and the one or more radio capabilities from the targetpeer wireless device; means for negotiating one or more compatible radioaccess technologies (RATs) available to use in a device-to-device (D2D)connection with the target peer wireless device according to at leastthe coexistence state and the one or more radio capabilities receivedfrom the target peer wireless device, wherein the means for negotiatingcomprises means for exchanging in-device and cross-device coexistencestates with the target peer wireless device; and means for establishingone or more D2D connections with the target peer wireless device usingthe negotiated one or more compatible RATs.
 20. The apparatus recited inclaim 19, wherein the means for negotiating the one or more compatibleRATs further comprises: means for determining that at least one of thecompatible RATs causes in-device interference at one or more of theapparatus or the target peer wireless device based on the exchangedin-device and cross-device coexistence states; means for negotiating amodified configuration associated with the at least one compatible RATto mitigate the in-device interference; and means for adjusting amulti-radio configuration according to the negotiated modifiedconfiguration associated with the at least one compatible RAT.
 21. Theapparatus recited in claim 19, wherein the means for negotiating the oneor more compatible RATs comprises: means for determining that at leastone of the compatible RATs causes cross-device interference at one ormore of the apparatus or the target peer wireless device based on theexchanged in-device and cross-device coexistence states; and means fornegotiating a modified configuration associated with the at least onecompatible RAT to mitigate the cross-device interference; and means foradjusting a multi-radio configuration according to the negotiatedmodified configuration associated with the at least one compatible RAT.22. The apparatus recited in claim 19, wherein the means for negotiatingthe compatible RAT comprises: means for determining that one compatibleRAT is available to use in the D2D connection with the target peerwireless device, wherein the one or more D2D connections with the targetpeer wireless device comprise one D2D connection established accordingto the one compatible RAT.
 23. The apparatus recited in claim 19,wherein the means for negotiating the one or more compatible RATsfurther comprises: means for determining that multiple compatible RATsare available to use in the D2D connection with the target peer wirelessdevice; and means for selecting one or more of the multiple compatibleRATs to meet a performance requirement associated with the D2Dconnection.
 24. The apparatus recited in claim 23, further comprising:means for deriving a priority list that orders the multiple compatibleRATs according to one or more policies that are based on one or more ofa user preference, a device state, or a mobile network operatorpreference, wherein the one or more of the multiple compatible RATs arefurther selected according to the derived priority list.
 25. Anon-transitory computer-readable storage medium havingcomputer-executable instructions recorded thereon, wherein executing thecomputer-executable instructions on a wireless device having one or moreprocessors causes the one or more processors to: request a radioconfiguration from a target peer wireless device, wherein the requestedradio configuration comprises a coexistence state and one or more radiocapabilities associated with the target peer wireless device; receivethe coexistence state and the one or more radio capabilities from thetarget peer wireless device; negotiate one or more compatible radioaccess technologies (RATs) available to use in a device-to-device (D2D)connection with the target peer wireless device according to at leastthe coexistence state and the one or more radio capabilities receivedfrom the target peer wireless device and in-device and cross-devicecoexistence states exchanged with the target peer wireless device; andestablish one or more D2D connections with the target peer wirelessdevice using the negotiated one or more compatible RATs.
 26. Thenon-transitory computer-readable storage medium recited in claim 25,wherein executing the computer-executable instructions on the wirelessdevice further causes the one or more processors to: determine that atleast one of the compatible RATs causes in-device interference at one ormore of the wireless device or the target peer wireless device based onthe exchanged in-device and cross-device coexistence states; negotiate amodified configuration associated with the at least one compatible RATto mitigate the in-device interference; and adjust a multi-radioconfiguration according to the negotiated modified configurationassociated with the at least one compatible RAT.
 27. The non-transitorycomputer-readable storage medium recited in claim 25, wherein executingthe computer-executable instructions on the wireless device furthercauses the one or more processors to: determine that at least one of thecompatible RATs causes cross-device interference at one or more of thewireless device or the target peer wireless device based on theexchanged in-device and cross-device coexistence states; and negotiate amodified configuration associated with the at least one compatible RATto mitigate the cross-device interference; and adjust a multi-radioconfiguration according to the negotiated modified configurationassociated with the at least one compatible RAT.
 28. The non-transitorycomputer-readable storage medium recited in claim 25, wherein executingthe computer-executable instructions on the wireless device furthercauses the one or more processors to: determine that one compatible RATis available to use in the D2D connection with the target peer wirelessdevice, wherein the one or more D2D connections with the target peerwireless device comprise one D2D connection established according to theone compatible RAT.
 29. The non-transitory computer-readable storagemedium recited in claim 25, wherein executing the computer-executableinstructions on the wireless device further causes the one or moreprocessors to: determine that multiple compatible RATs are available touse in the D2D connection with the target peer wireless device; andselect one or more of the multiple compatible RATs to meet a performancerequirement associated with the D2D connection.
 30. The non-transitorycomputer-readable storage medium recited in claim 29, wherein executingthe computer-executable instructions on the wireless device furthercauses the one or more processors to: derive a priority list that ordersthe multiple compatible RATs according to one or more policies that arebased on one or more of a user preference, a device state, or a mobilenetwork operator preference and select the one or more of the multiplecompatible RATs according to the derived priority list.